Deposition of rubber on the windings of magnetizable cores



May 21, 1946. F. J. SIGMUND ET AL DEPOSITION OF RUBBER ON THE WINDINGS OF MAGNETIZABLE CORES Filed March 28, 1942 5 Sheets-Sheet 1 IN V EN TORS hwk T BY 00M 5. Mu-L.

% ML W y 1946- F. J. SIGMUND ET AL 6 DEPOSITION RUBBER ON THE WINDINGS OF MAGNETIZABLE CORES Filed March 28, 1942 5 Sheets-Sheet 2 HI l ll ill INVENTORS ru-k T & BY WM (41w MMM MMW y 1946- F. J. SIGMUND ET AL 2,400,576

DEPOSITION OF RUBBER ON THE WINDINGS OF MAGNETIZABLE CORES Filed March 28, 1942 5 Sheets$heet 5 59 JNVENTORS 7PM I 8, BY )4 11%" S. M

yw w Mango Patented May 21, 1946 DEPOSITION OF RUBBER ON THE WINDINGS OF MAGNETIZABLE CORES Frank J. Sigmund and William S. Hlavin, Cleveland, Ohio, assignors, by mesne assignments, to Sigmund Corporation, a corporation of Ohio Application March 28, 1942, Serial No. 436,654

2 Claims.

The invention relates to elect p-deposition of rubber-like substances and par cularly to the electro-deposition of rubber-like substances on the windings of electrical devices.- This application will be described with reference to a stator for a dynamo-electric machine, but it is to be understood that the invention in its broadest scope is not limited to dynamo-electric machines. The stator herein disclosed and described is particularly useful in the submersible type of motor employed to drive, for example, a pump located in a well or other similar place.

An object of the invention is the provision of a magnetizable corefor an electrical device where in the winding is completely surrounded with electro-deposited rubber-like substance to render the winding fluid tight.

Another object of the invention is the provision of making a fluid tight winding for an electrical device by electro-depositing rubber-like substance upon the winding.

Another object of the invention is the provision of electro-depositing rubber-like substance completely around the coils of the winding located in slots of the magnetizable core of a dynamo-electric machine as well as the coil head and the terminal conductors in one complete electro-deposition process.

Another object of the invention is the provision of driving off the water from the deposited rubber-like substance by electro-endosmosis by using the winding as a positive pole.

Another object of the invention is to use the coils of the winding to generate heat for vulcanizing the deposited rubber about the winding.

Another object of the invention is the provision of obtaining vulcanization of the deposited rubber-like substance by subjecting the same to heat generated by current flowing through the winding upon which the rubber-like substance is deposited.

Another object of the invention is the provision of covering .or coating the winding of the electrical device with a material which has the property of strongly adhering the 1 rubber-like substance electrophoretically deposited thereon, in which the coating may, for example, comprise zinc, lead, cadmium, tin antimony, and their alloys.

Another object of the invention is the provision of providing on the outside of the winding a cotton covering or any other suitable porous nonconducting substance on which'the rubber-like substance may be deposited.

Another object of the invention is the improvement of electro-depositing the rubber-like sub- Another object of the invention is the provision of screw conveyor means to direct the circulation of the aqueous dispersion of the rubber-like substance into the slots of the stator upon the wind- Another object of the invention is the provision of a pump and a conduit having a slit therein substantially coinciding with the longitudinal openings of the slots of the stator to direct the circulation of the aqueous dispersion of the rubber-like substance upon the coils in the slots.

Other objects and a fuller understanding of the invention may be had by referring to the following description, taken in conjunction with the accompanying drawings, in which:

Figure 1 represents a perspective view of a stator of a dynamo-electric machine having a winding arranged to be covered with a fluid tight rubber-like substance;

Figure 2 is a fragmentary and enlarged crosssectional view of the stator showing but a single slot having a winding therein as it appearswhen the stator is immersed in a liquid or aqueous dispersion of rubber-like substance;

FigureS is a view of a liquid container having an aqueous dispersion of rubber-like substance with the stator immersed therein during the process of electro-depositing the rubber-like substance upon the winding of the stator;

Figure 4 is a fragmentary and enlarged view similar to Figure 2 but with the rubber-like substances being illustrated as deposited upon the winding of the stator;

Figure 5 is a fragmentary and enlarged view of the wire for the winding of the dynamo-electric machine in which the wire is illustrated as being coated with a suitable anode material having a cotton covering or other porous substance of an insulating character;

Figure 6 shows a perspective view of a spacer which is arranged to be mounted in the slots of the stator tokeep the winding from touching or contacting the stator prior to electro-depositing the rubber-like substance around the winding 01. the stator;

Figure 'l is a view similar to Figure 4 wherein a non-magnetic wedge having a plurality of holes and slots therein through which the aqueous dis-- persion of rubber-like substance maypass during the electro-depositing of the rubber-like substance upon the winding of the stator.

Figure 8 is a fragmentary and perspective view of the wedge shown in Figure 7;

Figure 9 is a fragmentary and enlarged view similar to Figures 2, 4 and '7 but shows a modiflcation of our invention in that a rubber-like sheet of material is mounted in the slot before the winding is inserted therein, after which the neck of the slot is closed by electro-depositing rubberlike substance across the open space between the sides of the neck of the slot;

Figure 10 is a fragmentary and side view oi the stator showing the winding and the out! of the rubber sleeve extending from the side of the stator;

Figure 11 shows a view similar to Figure 10 wherein the winding of the coil head is coated with material rendering the 'coil head suitable for the depositing of rubber-like substance thereon in an electro-deposition process; A

Figure 12 is a fragmentary and enlarged view of a slot, something like the view in Figure 2, but shows in addition thereto a longitudinal opening extending through the core in the region of the bottom, and in communication with, each windingslot;

Figure 13 shows a diagrammatic and crosssectional view of a container with the stator and rubber-coated winding thereon immersed in a conducting bath or body to drive of! from the depositedrubber-like substance on the winding at least a part of the water content by electroendosmosis by passing an electric current through the deposited rubber-like substance by direct application of a conducting body to the surface thereof with the winding serving as a positive pole;

Figure 14 is a view similar to Figure 3 but shows in addition thereto a plurality of vertical tubes having slits therein which coincide substantially with the longitudinal openings of the slots of the stator for controlling the circulation of the aqueous dispersion of rubber-like substance in direct contact with the winding in the slot;

Figure 15 is a view somewhat similar to Figure 2 but shows the circulation of the aqueous dispersion of rubber-like substance flowing around the winding in the slot as conducted b the tubes shown in Figure 14;

Figure 16 is a perspective view of the tubes shown in Figure 14 wherein the tubes shown in 16 are the tubes which are insertable in the longitudinal opening which is in .communication with the bottom of the slots of the stator;

Figure 17 is a view somewhat like Figure 14 except that screw conveyor means are employed to circulate the aqueous dispersion of rubber-like substance through the slots of the stator; and

Figure 18 is a view similar to Figure 15 showing the circulation of the aqueous dispersion of rubber-like substance as effected by the screw conveyor means shown in Figure 1'1; and

Figure 19 is a fragmentary view showing a modified arrangement for removing the water from the wires of the coils which are enveloped with a deposit of rubber-like substance.

The term rubber-like substance as used herein includes natural latices such, for example, as rubber, guttapercha and balata, or synthetic latices such, for example, as polymers or butadiene or other diolefins, which if desired, may be concentrated and/or vulcanized or artificial aqueous dispersions prepared from the said substances or from waste rubber or reclaimed rubber. These dispersions may be, if desired, combined or mixed with additional substances as for example fillers, dyes, vulcanizing substances, accelerators, etc.

In this application, the anode is the element on which the rubber-like substance is deposited.

With reference to the drawings, Figure 1 illustrates a stator 2| for a dynamo-electric machine having a plurality of coils 2i to which terminal conductors 22 may be suitably connected. As shown in Figure 2, the coils are inserted in the slots of the stator in accordance with the common practice of making stators for dynamo-electric machines. The coil slots are indicated by the reference character 23 and may be of the openslot type having a reduced opening or neck 24. In usual practice, the coils are preferably preformed and the wires which compose the coils are inserted through the open neck 24 in small groups or in small numbers until the complete coil is mounted in each of the slots.

The entire stator with the winding thereon as shown in Figure l is immersed in a tank 25 having an aqueous dispersion of rubber-like material 26. As illustrated, the inside of the tank 25 is provided with brackets 28 which extend radially inwardly of the tank to engage the lowermost outside edge of the stator for supporting the stator in the tank. Extending vertically upward centrally of the tank 25 is a central post 29 which passes through the large central opening of the stator. In mounting the stator in the tank 25 the stator is lowered with the large central opening of the stator surrounding the central post until the bottom of the stator engages the bracket 28. That is to say, in the mounted position the inside surface of the large opening .of the stator is substantially concentric with the central post 29, see the fragmentary showing in Figure 2. After the stator is positioned in the tank 25 a plate 30 is placed above the coil head of the stator and may be held at a spaced distance from the coil head by a set screw II which is arranged to engage the central post 2! and adjustably hold the plate 30 in any position relative to the top of the coils of the stator. In the practice of our invention, the tank 25, the core 20, the central post 29, and the top plate 30 are all electrically connected and constitute the current. Therefore, as shown in Figure 3 the conductor 42 may be connected to the negative side of the line and the conductor ll may be connected to the positive side of the line of a suitable source of current. During the electro-deposition process, the aqueous dispersion of rubber-like substance may be kept in gentle circulation by means of a pump 32 which is fed by a pipe 33 connected to the upper portion of the tank and which delivers the aqueous dispersion of rubber-like substance to the bottom of the tank through a pipe 34. The pump 32 is of the type which gives a gentle movement to the aqueous dispersion of rubber-like substance in order to keep it in the proper condition for electro-deposition.

In this invention, the tank 25 is arranged to be evacuated during the electro-deposition process. To this end the tank 25 is provided with a cover 35 having a gasket 36 positioned between the top edge of the tank 25 and the underneath edge of the plate 35 to render the tank air-tight. The tank 25 may be evacuated by a vacuum pump 31 to which is attached a gauge 38 showing the degree of the vacuum maintained within the tank. The cover 35 may be provided with a valve 39 to admit atmospheric pressure through the top of the tank during the electro-desposition process.

Throughout the period of electro-deposition, we preferably evacuate the tank to extract all of the gases and air from the tank after which the vacuum is destroyed by opening the valve 39 which admits atmospheric pressure to the top surface of the aqueous dispersion of rubber-like substance which forces the aqueous dispersion of rubber-like substance together with the deposited rubber-like substance upon the winding in all of the interstices of the winding in the slots of the stator. Throughout the process the vacuum pump .31 and the valve 39 may be operated in alternate sequences so that several applications of atmospheric pressure may be applied to insure complete and perfect disposition or deposition'of the rubber about the winding in the slots of the stator. The differential pressure between vacuum and atmosphere funtions to cause the rubber-like substance to make a complete envelope about the windings within the slots as well as the windings of the coil heads on each end of the stator. In Figure 4 we show the deposited rubber-like substance as being indicated by the reference character 40 and completely envelopes the wires which comprise the coils in the slots. In actual practice, the rubber-like substance may be drawn into the fine spaces and cracks between the individual wires rendering the entire coil in each slot perfectly insulated from the core as well as being absolutely fluid-tight to enable the stator to be used in a submersible pump.

In the practice of our invention We preferably coat the copper wire used for the winding with an anode material which may comprise zinc, lead, cadmium, tin antimony and other alloys of like nature. In Figure 5 the reference character 44 represents the copper wire and the reference character 45 represents the anode material surrounding same. On the outside of the anode material 45 we preferably-made a double serving of cotton or any other suitable porous non-conducting material. The cotton or the other suitable porous non-conducting material is indicated by the reference character 46. Prior to the insertion of the wires in the slots, we preferably position at spaced distances along each of the slots a spacer 41 as shown in Figure 6 which may be constructed of rubber-like substance. The spacer 41 is arranged to keep the wires spaced from the core of the stator and may be. spaced at any suitable distances along each of the slots to give sufficient support to the wires to keep them from contacting the edge of the inside surface of the slots. The spacers 41 are preferably made out of rubber-like substance so that the deposited rubber-like substance may be bonded or welded directly thereto to make a continuous homogeneous mass of rubber about the coils, In order to make a good bond between the'edges of the spacers 41 and the electro-deposited rubber-like substance the side edges 43 of the rubber spacers 41 may be coated with a suitable rubber cement or other bonding material to give a good bond and thereby make a fluid tight envelope about the winding.

In certain size motors or dynamo-electric machines, it may be preferable to secure the coils in the slots with sufficient mechanical security to prevent the wires from coming out of the neck 24 of the slot. In these cases, we preferably use a porous and non-magnetic wedge 48 for the neck of the slots, see Figures 7 and 8. The wedges may be made of an suitable non-magnetic material and may also be of an insulating nature. As illustrated, the wedges are arranged to be provided with a plurality of openings 49 and grooves 50 so that there is free communication of the aqueous dispersion of rubber-like substance therethrough during the electro-deposition process. Consequently, during the electro-deposition process the aqueous dispersion of rubber-like substance is attracted toward the winding through the holes and grooves in the wedges. The actual disposition of the holes and the grooves may be of any general arrangement and in fact the holes and grooves may be larger than those shown in the drawing. The deposition of the rubber for Figure 7 is the same as that for Figure 4 and in Figure 7 the employment of the alternate application of the vacuum and the admission of atmospheric pressure to the top of the tank is particularly useful in order to make a perfect envelope of rubber-like deposit around the winding inside of the slots.

In Figures 9, l0 and 11 we show a modified arrangement of enveloping the windings in the slots of the stator in that we eliminate the electrodeposition of the rubber-like substance around the windings in the slot and use a sheet of rubber-like substance 53 instead. In this modified form of our process, the sheet of rubber 53 is first inserted into the slots after which the windings are mounted therein in accordance with the usual practice. After all of the wires are inserted in the slots the top of the slot is mechanically closed off b a wedge 54 which is of a non-magnetic material. The wedge 54 prevents the wires from coming out of the slots, In addition, the wedge 54 may be made of a suitable anode mate rial such, for example, as zinc or any other material and in this process it becomes an anode for electro-depositing rubber between the two ends of the sheet of rubber in the neck of the slot. The rubber which is deposited upon the wedge 54 as an anode is illustrated by the reference character 55 and completely closes the opening across the neck of the slot between thetwo ends of the rubber sheet. The inside surfaces of the ends of the rubber sheet may be precoated with a suitable cement or other bonding material in order to facilitate the bond between the deposited rubber 5-5 and the sheet of rubber 53 to make a perfect fluid tight joint. As shown in Figure 10, the ends of the sheet of rubber 53 are brought out beyond the side of the stator core 20 to provide cuifs 52. The next major step in the Process shown in Figures 9, l0 and 11 is to electro-deposit rubber-like substance upon the coil heads 58 of the winding. To do this we preferably coat the coil heads with a suitable resin which may be indicated by the reference character 59 and which in itself may be electrically conducting to become an anode for electrically depositing a rubber-like substance upon the coil head by immersing the stator in a suitable body of aqueous dispersion of rubber-like substance. In order to render the process more efficient, the outside of the resin 59 may be coated with zinc powder which is indicated by the reference character 80 which becomes a perfect anode for the electro-deposition of the rubber-like substance upon the coil head when the stator is immersed in a body of aqueous dispersion of rubber-like substance. Before immersing the stator in the body of aqueous dispersion of rubber-like substance the edges ii of the cuff of the rubber sheet I3 may be coated with a suitable rubber cement or other good bonding material to give a good bond or weld between the electro-deposited rubber and the cuff of the sheet of rubber 53. In the process shown in Figures 9, and ii the conductor terminals 22 are also treated and coated with rubber-like substance in the same fashion as that described with reference to the coil heads 58. The entire process produces fluid-tight windings and terminal conductor leads for the stator.

In Figure 12 we show a further modified form in the process of electro-depositing rubber-like substance about the wires in the slots of a dynamo-electric machine in that we provide a longitudinal opening which extends from one end of the stator to the other in the region of the bottom of, and in communication with, each winding slot. The longitudinal opening is lndicated by the reference character 64 and may be preferably round which permits the aqueous dispersion of rubber-like substance to flow in direct communication with the bottom of the slots. The longitudinal opening 64 constitutes another measure to render a complete fluid tight rubberlike envelope about the wires within the slots. Another advantage of the longitudinal opening 64 is that they effectively increase the cooling area of the stator during operation. As mentioned hereinbefore. the fluid tight winding for a stator makes the stator suitable for submersible pumps in which design the fluid pumped by the fluid pump in the well or other liquid, i drawn upwardly through the longitudinal opening 64 which makes a very efficient method for cooling the stator. The bottom of the slots of the stator become relatively hot during operation and we therefore place the longitudinal opening at the bottom of the stator, at what might be called the hot spot of the stator. The drawing of the liquid which is being pumped by the submersible pump through the longitudinal opening 64 gives very effective distribution of heat in the stator or rather a very good dissipation of the heat from the stator. Accordingly, the longitudinal opening 64 not only serves as a conduit for directing the aqueou dispersion of rubber-like substance through the bottom of the slots during the electro-deposition process, but also function as conduits through which liquid may be moved by the submersible pump for cooling the motor while driving the pump.

After the rubber-like substance has been deposited upon the wires of the stator the next operation is to drive off the water content in the rubber-like deposit. This may be done by a process called electro-endosmosis by passing an electric current through the deposited rubberlike substance by direct application of a conducting body to the surface thereof with the coils serving as a positive pole. This arrangement is shown in Figure 13 in which the stator 20 and the winding with the rubber deposit thereon is immersed into a tank 85 having an electroconductive liquid 81 therein. The conductive liquid 81 may be of mercury or any other suitable electro-conductive material. The stator may be supported within the tank 65 upon suitable brackets 66. The coils of the winding of the stator serve as a positive pole and may be connected to a positive source of current by a conductor Ill. The electro-conductive material 01 in the tank may be charged negatively by means of an element 68 immersed in the electroconductive material 61 and connected to the negative side of a suitable source of current through the conductor 69. The direct application of the current through the deposited rubber upon the winding drives of! at least a major part of the water content thereof by electro-endosmosis. The surface moisture and the residual moisture may be removed by one or more drying processes by inserting the stator in an air drying chamber. The vulcanization of the deposited rubber-like substance will be effected without further treatment, at ordinary temperature and in a relatively short interval of time provided a suitable accelerator is used in the dispersion. If immediate vulcanization is desired the deposit may be subjected to heat as by electrical current flowing through the wires of the winding.

In Figures 14, 15 and 16 we show a method for obtaining good control of the circulation of the aqueous dispersion of rubber-like substance during the electro-deposition process. In Figure 14 the central post 13 is provided with a plurality of annularly spaced longitudinal slits 14 which are in substantial alignment with the longitudinal opening of the slot. In addition, we employ a plurality of vertically arranged tubes 15 in which each has a longitudinal slot l! which is substantially in alignment with the opening of the bottom of the slots of the stator. The longitudinal tubes are indicated by the reference character 15 and are connected to a manifold I6. The circulation of the aqueous dispersion of rubber-like substance is accomplished by a pump I8 which is fed by a pipe 19 connected to the upper portion of the tank 25. The

outlet of the pump 18 is connected toa feed pipe which delivers the aqueous dispersion of rubber-like substance through the valves 8|, 82 and 83. The valve Bl controls the flow of the aqueous dispersion of rubber-like substance through a pipe 84 to the manifold I8, where in turn the aqueous dispersion of rubber-like substance is conducted vertically up through the tubes I5 and out through the longitudinal slit 1! into the bottom of the slots of the stator, see Figure 15. The valve 82 controls the flow of the aqueous dispersion of rubber-like substance to the inside of the hollow post 13, where the materlal is distributed out through the longitudinal slit H which directs the aqueous dispersion of rubber-like substance into the slots through the restricted neck 24. The valve 83 controls the flow of the aqueous dispersion of rubber-like substance into the tank itself. The circulation of the aqueous dispersion of material is gentle and is such as to maintain the material in proper condition for electro-deposition. The top of the tubes 15 is closed so that the aqueous dispersion of rubber-like substance is caused to flow out of the longitudinal slits or slots 11.

In Figures 17 and '18 we show another arrangement for controlling the flow of the aqueous dispersion of rubber-like substance to the winding '64 may be closed by suitable stoppers 91.

in the slots of the stator. In Figures 17 and 18 we employ a screw conveyor 81 in the large central opening of the stator and a plurality of screw conveyors 89 in each-of the longitudinal openings 64 at the bottom or the slots. The screw conveyors may be driven in any suitable manner such as individually by electric motors or by a system of gears indicated generally by the reference characters 92 and 93, in which the gears 93 drive a shaft 9| for actuating the screw conveyors 89 and in which the gear 92 actuates a shaft 96 for driving the main screw conveyor 81. The system of gears may be driven by a shaft 86 which in turn may be driven by a motor of any suitable nature. A seal 94 may be employed to seal the shaft 90' in the bottom of the tank and seals 95 may be employed to seal the shaft 9| in the bottom of the tank. The top of the large opening in the stator itself may be closed by a stop plate 96 and the top of the openings The screw conveyors 81 and 89 as well as thetank 25 and the stator '20 constitute the cathode for the electro-deposition process and as illustrated the shafts 96 and 9| which drive the screw conveyors may be connected to the negative side of the line 42 through a conductor 98.

The employment of the vacuum in the devices shown in Figures 14 and 17 is the same as that hereinbefore described with reference to Figure 3, wherein the vacuum not only operates to force the rubber-like deposit completely around the winding as a result of the diflerential pressure between the vacuum and atmosphere but also functions to remove the gases to improve the electro-deposition process.

The longitudinal openings 64 besides functioning to aid in dissipating the heat from the hot spot of the stator during the operation of the dynamo-electric machine also serves, during the vulcanization of the rubber, as conduits to direct air in intimate contact with the deposits in the bottom of the slots.

In Figure 19 we show another method of removing the water content from the wires of the coils inside of the rubber-deposited envelope in addition to the method already described involving the electro-endosmosis method of removing the water. In Figure 19 we show a tube 62 of a suitable material located longitudinally in the slot 23 of the stator at the same time that the wires are inserted in the slots. In Figure 19 the wires themselves are not shown for clarity purposes. The tube 62 may extend from one end of the stator to the other with one end 12 thereof extending out beyond the wires where they make the bend for the coil heads. The rubber-like substance 40 may be deposited around the wires in the same manner as hereinbefore described, using the vacuum to remove the gases and air and to give a good layer of the rubber deposit completely around the winding in the slots and the coil heads. The small openings 63 are filled with paraihn or other fusible material so that during the evacuation process which is carried on during the electro-depositing of the rubber, the openings 63 are not filled by the rubber deposits themselves.

During the extraction of the water from the wires which are enveloped in the rubber deposit, the paraflin is melted from the opening 63 by the application of heat which may be generated by passing current through the windings themselves.

Subsequent to the opening of the holes in the tube 62, a vacuum may be applied to the extension tube 1| which is inserted over the end 12 of the tube "for withdrawing the moisture from inside of the, rubber envelope. The melted paramnor other material may also be withdrawn from the tube 62 at the same time that the water is withdrawn from inside of the rubber envelope about the wires. As a method for testing the rubber envelopes about the wires for leakage, pressure may be applied to the extension tube II and any leakage of the rubber envelope may be determined by immersing the entire stator under water very much' in the same fashion that an inner tube is tested for an automobile. Also, hot

air may be injected inside of the rubber envelope around the wires through the opening 63' by introducing hot air through the extension tube I I.

In this manner, the wires may be completely dried for safe operation When the wires have been completely dried, the tube 62 may be cut off flush with the rubber deposit 40 or may be completely withdrawn from the wires after which the opening in the rubber envelope may be vulcanized or patched over very much in the same fashion as closing punctures in a rubber inner tube.

Although we have described our invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

We claim as our invention:

1. A method of producing a fluid-tight winding for a magnetizable core having slots there through, comprising the steps of coating a copper wire with a metal of the class consisting of zinc, lead, cadmium, tin, antimony, and alloys to which electrophoretically deposited rubber will readily adhere, covering said coated wire with porous non-conducting cloth material, winding said coated and covered wire through the slots of the magnetizable core with the wire looped around the ends of the core, preparing terminal conductors with a coating of a metal of the class consisting of zinc, lead, cadmium, tin, antimony, and alloys to which electrophoretically deposited rubber will readily adhere, covering thevprepared terminal conductors with a porous non-conducting cloth material, attaching the prepared terminal conductors to the wires in the slots, and thereafter waterproofing the winding and the terminal conductors by electrophoretically depositing on them an insulating material of the class consisting of natural and synthetic rubber from their latices to a thickness suflicient to render the said winding fluid tight when the said insulating material is dried and vulcanized, and thereafter drying and vulcanizing the deposited insulating materials thereon to produce a fluidtight winding.

2. A method for producing a fluid-tight winding for a magnetizable core having slots therethrough, comprising the steps of coating a copper wire with a metal of the class consisting of zinc, lead, cadmium, tin, antimony, and alloys to which electrophoretically deposited rubber will readily adhere, covering said coated wire with porous non-conducting cloth material, winding said coated and covered wire through the slots of the magnetizable'core with the wire looped around the ends of the core, preparing terminal conductors with a coating of a metal ofthe class consisting of zinc, lead, cadmium, tin, antimony, and

alloys to which electrophoretlcally deposited rubber will readily adhere, covering the prepared terminal conductors with a porous non-conductin; cloth material, attaching the prepared terminal conductors to the wires in the slots, and thereafter waterproofin the winding and the terminal conductors by placing the wound magnetizable core in a container or a dispersion or insulating materials of the class consisting of latices 0! natural and synthetic rubber, evacuat- 10 ing said container, and thereafter electrophoretically depositing said insulating material on the said windings and terminal conductors to a thickness sumcient to render thesaid winding fluidtight when the said insulating material is dried and vulcanized, and thereafter drying and vulcanizing the deposited insulating materials thereon to produce a fluid-tight winding.

FRANK J. SIGMUND.

WILLIAM S. HLAVIN. 

